RU101712U1 - DEVICE FOR DECOMPOSITION AND SINING OF MINERAL RAW MATERIALS - Google Patents

Abstract

 A device for the decomposition and sintering of mineral raw materials, consisting of nodes for loading the feedstock, unloading the target product and removal of conversion gases, a decomposition zone and sintering of the feedstock, means for supplying the feedstock to the decomposition zone, characterized in that the means for supplying the feedstock to the decomposition zone and sintering is made in the form of a closed belt conveyor, at one end of which a feedstock loading unit is installed in the form of a hopper with a dispenser, and at the other end, the target product unloading unit is made In the form of a receiving hopper, an electron accelerator is installed above the decomposition and sintering zone of the feedstock, under which a protective cap is mounted, connected by a pipeline to the means for pumping conversion gases.

Description

The utility model relates to the chemical industries, where the processes of dissociation and sintering of solid mineral, in particular, carbonate raw materials are used. Carbonate decomposition products are used in metallurgy, construction industry, pulp and paper and sugar industries, in the production of fertilizers for agriculture, etc. The technology of building materials is based entirely on the burning of carbonate raw materials. At the same time, a number of physical and chemical transformations take place in the material being fired, among which the decomposition of carbonates and other complex molecules, drying, swelling, sintering, and others are worth noting.

Raw materials are fired in specially designed furnaces for these purposes. By their design, these furnaces differ radically, based on the principle of converting the energy of energy carriers used into thermal energy: plasma energy, electron beam energy, microwave energy and energy of combustible fuel. Let us consider in more detail the principle of operation of these furnaces, their scope, advantages and disadvantages.

1. Plasma-thermal furnaces. In plasma-thermal furnaces, low-temperature plasma energy with kinetic electron energies of up to 10 eV is used as a coolant. This value of kinetic energy does not allow electrons to penetrate deep into matter to any noticeable depth. Therefore, these furnaces are not used for firing in the building materials industry and are effective only for the production of gaseous products and powders for functional purposes (titanium dioxide, ultrafine titanium nitride, silicon nitride, etc.) / (Yu.P. Udalov. “Processes and devices chemical technologies. ”Part 2., Website: www.naukaspb.ru)

2. Electron beam furnaces. They are an electronic gun, the cathode of which is supplied with an electric voltage of 10-40 kV. The gun works in a vacuum. The capacity of these furnaces reaches 8 MW. As in the previous case, due to the small kinetic energy of the electron beam, this furnace is not used in the technology of building materials. It is effective in vacuum smelting of metals.

References: TSB “Electron Beam Furnace”.

3. Microwave ovens. The raw materials to be fired are heated in these furnaces by microwave electromagnetic radiation. The scheme of decomposition and calcination of carbonates

It looks like this: fractionated raw materials are fed into the bunker, from where it enters the microwave cavity (reactor), where the dissociation reactions take place and sintering occurs after electromagnetic radiation is supplied to this reactor through the waveguide. Conversion gases are pumped from the upper part of the reactor through special fittings. The creation of a constant rarefaction in the reactor increases the conversion of carbonates, since a decrease in pressure leads to a shift in the reaction equilibrium towards the decomposition reaction.

In the well-known installation "Electrodynamic microwave installation for the decomposition of calcium carbonate" (Bikbulatov I.Kh., Deminev R. R., Shulaev N.S. and others. Patents of the Russian Federation No. 2170138, No. 2111626), the problem was solved of reducing energy consumption, increasing conversion, and the quality of products reducing environmental pollution. The use of microwave microwave radiation as an energy carrier, according to the authors, frees the process of carbonate decomposition from the use of various fuels, from initiating side reactions due to contact with the fuel and furnace material, provides volumetric heating of the raw material. The results of experiments with a sample of calcium carbonate weighing 38 g, conducted on this installation, also showed that its efficiency is 15% higher than a traditional lime kiln. Similar results were obtained by Bakhonin A.V. (Abstract of the dissertation “Development of apparatus designs for mass transfer processes using microwave electromagnetic radiation”, Publishing House of Ufa State National Technical University. 2003)

Also known is the "Installation for firing hydromica" (RF Patent No. 2171552), which solved the problem of dehydration of mica with different water contents.

Despite the positive results, it is not possible to draw a conclusion about the prospect of using this method in various chemical technologies, primarily for the following reasons:

- the method has a fundamental limitation of application due to the fact that various substances, depending on the physical nature, absorb or not absorb electromagnetic radiation at all; materials intended for heating and firing should have a large value of the coefficient of dielectric loss (product of the dielectric constant by the tangent of the loss angle), since otherwise the power dissipated in the dielectric will be insufficient for heating and firing; - the fundamental technical difficulties of loading and unloading large masses of matter into resonators under conditions of supplying high microwave power to these resonators;

- problems with electric strength in resonators and supply waveguides at high power levels of microwave radiation;

- absorption of part of the microwave energy in the input waveguides, resonators and loads - microwave.

In our opinion, plants based on this energy carrier have a great prospect for dehydration, drying, etc. because wet materials have a high dielectric loss coefficient.

4. Thermal furnaces. They are the main kiln units used in the technology for the production of building materials. In view of the similarity of the main raw materials (in the production of lime - limestone, in the production of cement - limestone and clay, in the production of expanded clay - clay, etc.) and processes during their heat treatment in the same equipment is used in these industries, which differs only in size and a set of auxiliary devices that are part of the furnace units: mine, bulk, rotating, fluidized-bed furnaces and cyclone ones.

(Yu.I. Dytnersky. Processes and devices of chemical technology. Publishing house. "Chemistry". 2002; A.V. Volzhansky. Mineral binders. M. Stroyizdat. 1986; Processes and devices of chemical technology. Website www.naukaspb.ru; Cement production in Russia in 2005-2010, Website www.iskitimcement.ru; Patents of the Russian Federation: 2101636, 2158402, 2205806, 2287496, etc.)

As a prototype that is closest to our proposal for purpose and versatility, we chose the firing of mineral raw materials in thermal furnaces, in particular, firing in a rotary kiln. Spy, I.P., Tsibin. Rotary kilns for the production of building materials; In the book "Processes and Apparatuses of Chemical Technologies", part 2, website www.naukaspb.ru).

A rotary kiln is a hollow cylinder or drum made of refractory steel, lined inside with refractory bricks (lining). The furnace body is located obliquely to the horizon at an angle of 3-6 degrees and rotates around the longitudinal axis with a revolution frequency of 1-4 revolutions per minute. This furnace unit includes a device for burning fuel, feeders, a refrigerator, dust collecting devices, etc. Raw material is supplied to the upper loading part, and a fuel burning device is placed in the lower unloading part. In these furnaces, natural gas, pulverized fuel (coal and shale) and fuel oil are predominantly burned. Due to the rotation of the drum, the raw material mass moves to the furnace head and through the connecting chamber it enters the refrigerator installed behind the furnace, and then to the storage bins. Conversion carbon dioxide due to convection or forced movement of air from the furnace head to the loading device moves upward along the inclined drum, mixes with the flue gas and goes into the atmosphere, or to a gas trapping device for further cleaning from the flue gas and subsequent disposal.

For decarbonization, for example, 1 mole of carbonate, in theory, 180 kJ is required. From a comparison of this value of the thermal effect of the reaction and operational data on the decomposition of such an amount of carbonate, it follows that the efficiency of the thermal process lies within 25%. Fuel consumption for decarbonization and sintering is significant and reaches 25-40 percent of the fired mass.

The disadvantages of the rotary kiln, most often used in the construction industry, include:

1. Extremely high energy consumption due to low thermal process efficiency and heat dissipation in furnace materials and the environment.

2. The huge costs of fuel equivalent and the high costs of delivering this fuel to the plants.

3. Poor product quality due to mixing of calcined raw materials with fuel and the presence of contact of raw materials with the material of the furnace structure, as well as the presence of unheated and overheated areas of the raw material due to non-uniform heating.

4. It is difficult to utilize the conversion of carbon dioxide due to the need to clean it from flue gases.

5. Large metal and material consumption of furnace designs.

6. The high cost of capital construction and construction space.

7. Huge pressure on the environment: heavy metals, carbon monoxide, nitrogen oxides, sulfides, heat dissipate into this environment, and ultimately, ash also gets into this environment.

Since all the thermal furnaces listed here use the same energy source as the rotary kiln considered here, the same disadvantages are inherent in them.

The objective of this utility model is to reduce the energy and material consumption of production, improve the quality of conversion products, metal oxides and carbon dioxide, reduce environmental pressure on the environment.

For this purpose, a device for the decomposition and sintering of mineral raw materials, consisting of nodes for loading raw materials, unloading the target product and removal of conversion gases, a zone of decomposition and sintering of raw materials, a means of supplying raw materials to the decomposition and sintering zone, and a means for supplying raw materials into the decomposition and sintering zone is made in the form of a closed belt conveyor, at one end of which a feedstock loading unit is installed in the form of a hopper with a dispenser, and at the other - a target unloading unit the product that has formed as a hopper over an area of the feedstock installed decomposition accelerator of electrons under which is mounted a protective cap coupled to the conduit means for pumping gas conversion.

The figure shows a General diagram of the device, where

1 - electron accelerator;

2 - electron beam;

3 - receiving hopper;

4 - dosing and forming device;

5 - a cap for collecting carbon dioxide conversion and protection against x-ray radiation;

6 - belt conveyor;

7 - adjustable drive;

8 - raw materials;

9 - a bin of finished products;

10 - pipeline;

11 - node pumping carbon dioxide and sending it to recycling;

12 - pipeline.

The principle of operation of a device based on a radiation energy carrier is as follows. When a substance is irradiated with electrons, if their kinetic energy is higher than the dissociation energy or the ionization energy of the molecules and atoms of this substance, ions and excited states of atoms are formed in the substance and, as a result, particles that cannot arise at low temperatures due to equilibrium processes. First of all, these are particles of decomposed carbonates and particles of the type: O, O ₂ , C, CO ₂ , etc. The energy of accelerated electrons spent on the production of these particles is ultimately converted to heat. The energy losses for dissociation and ionization significantly exceed the energy losses for bremsstrahlung at electron energies of the order of megaelectron-volt units and should not be taken into account (Yu, M, Shirokov NP Yudin. Nuclear Physics. Publishing House Nauka M. 1972).

The absorption of electron energy occurs instantly, uniformly throughout the volume and only where the electron beam interacted with the substance. In the case where relaxation times, i.e. the times of a system returning from an excited state to a normal state are much longer than the times of physical action, which is characteristic of a condensed state of matter, it becomes possible to control the yield of chemical forms and phases even in nonequilibrium systems and shift them to lower temperatures.

To implement this device, it is possible to use industrial electronic accelerators with electron energies from 10 keV to 10 MeV. The lower value of the indicated energy range is due to the fact that even at this energy, the process of dissociation and ionization is effective, since at these energies the ionization cross section is maximum. The upper value is due only to the requirement not to create the so-called induced radioactivity, which appears as a result of photonuclear reactions in irradiated materials mainly at energies above 10 MeV. The most suitable, in our opinion, is an ELV-12 accelerator with the following parameters: energy - 1 MeV, power in the beam - 400 kW, efficiency - 90%. It can be placed indoors 5 × 5 × 6 m ³ . This is an industrial accelerator, fully automated and successfully operated in the national economy in Russia and abroad. Accelerators of this series are designed and manufactured at the Institute of Nuclear Physics RAS, in Novosibirsk.

(Salimov R.A. ELV Series Accelerators and Their Application in Radiation Technological Processes and Medicine. Materials of the 10th International Meeting. St. Petersburg. 2001).

The proposed device (see figure 1) works as follows. Raw material 8, crushed to a particle size of about 1 mm, is loaded into a receiving hopper 3, installed near the electron accelerator 1, using a metering and forming device 4, a mass of raw materials equivalent to the production capacity is evenly distributed on a closed conveyor belt, along the width and thickness of the backfill, moreover, the width and thickness of the backfill are constant, since the sweep width of the electron beam and its energy do not change. After that, an adjustable drive of the conveyor belt 7 is turned on and raw materials are supplied under the electron beam 2, and then after irradiation the finished product enters the hopper 9 for cooling or storage. In the irradiation zone of raw materials between the accelerator and the conveyor, a cap 5 is installed that isolates the irradiation zone from the environment. The cap 5 is connected by a pipe 10 to the pumping unit 11 of conversion carbon dioxide and its direction through the pipe 12 for disposal.

The firing power of raw materials is estimated from the expression:

M = P / (C _beats × T), where

P is the power of the electron beam, C _beats is the specific heat of carbonate. T is the temperature. For lime production at Р = 400000 W, С _beats = 835 J / kg × degree, Т = 1200 ° С

M = 0.4 kg / s.

For cement firing, this value will be slightly lower due to a higher firing temperature of 3.4 kg / s. The feed rate under the beam is determined by the formula:

V = P / (C _beats Tdab). Where

d is the density, a is the width of the conveyor belt, b is the thickness of the backfill, the remaining designations are the same. For lime production (T = 1200 degrees Celsius)

at a density equal to 1500 kg / m ³ (transparency coefficient of crushed limestone is taken into account), conveyor width - 1.5 m and backfill thickness 0.5 cm

the feed rate will be approximately 0.035 m / s (128 m / h), and for cement production - 0.03 m / s (110 m / h)

It follows from the above expressions that a device based on a radiation energy carrier consumes energy for the production of 1 kg of calcite 1786 kJ

(400 kJ / (0.56 × 0.4 kg / s) at hourly and daily output of 810 kg and 20 tons, respectively.

The table shows the comparative characteristics of devices for the decomposition and sintering of mineral raw materials.

Table options radiation thermal Displacement equilibrium decomposition reactions Towards low temperatures Towards high temperatures Nature of heating Instant and uniform throughout the volume Inertial and uneven throughout Coefficient of performance, %% 90 25 Efficiency, rel. units one 0.28 Consumption of fuel equivalent,% of output 0 25-40 The presence of impurities Only natural Natural and technological Carbon dioxide Clean Requires complex and expensive cleaning measures Environmental pressure on the environment 0 Ash, heavy metals, harmful gases, heat dissipation, etc.

In conclusion, we note that currently Russia produces cement and lime 80 and 10 million tons annually. According to OAO IskitimCement, depreciation of the active part of fixed assets at most enterprises exceeded 70%. 93.5% of furnaces with a service life of more than 30 years are in operation. The ongoing and planned modernization proceeds from the improvement of furnaces and their units, while the basic and fundamental question of the low efficiency of the thermal process remains unshakable. Therefore, the modernization of these industries using new and environmentally friendly energy carriers seems to us an extremely important strategic direction. Accelerators recommended by us provide continuous continuous operation in industrial production. They are simple in design, easy to operate, reliable in operation, fully automated and constantly improved. Modular designs are allowed, due to which it is possible to significantly increase the capacity of plants built on this proposal.

Claims (1)

A device for the decomposition and sintering of mineral raw materials, consisting of nodes for loading the feedstock, unloading the target product and removal of conversion gases, a decomposition zone and sintering of the feedstock, means for supplying the feedstock to the decomposition zone, characterized in that the means for supplying the feedstock to the decomposition zone and sintering is made in the form of a closed belt conveyor, at one end of which a feedstock loading unit is installed in the form of a hopper with a dispenser, and at the other end, the target product unloading unit is made In the form of a receiving hopper, an electron accelerator is installed above the decomposition and sintering zone of the feedstock, under which a protective cap is mounted, connected by a pipeline to the means for pumping conversion gases.